Bell-type nozzle blow-molding installation

ABSTRACT

A blow-molding installation for manufacturing receptacles from blanks of thermoplastic polymer, said installation comprising a bell-nozzle for blowing a fluid under pressure into a blank ( 3 ) disposed in a cavity ( 2 ) of a mold ( 1 ), the end of the nozzle being in the shape of a bell ( 11 ) which is suitable, during blow-molding, for being pressed into leaktight end-to-end abutment against a wall (F) of the mold while capping the neck ( 7 ) of the blank that emerges from said wall; said installation further comprises means ( 16   1 ) for securing the nozzle to the wall of the mold by mutual attraction, which means can be activated, after the nozzle has been brought into end-to-end contact with the wall (F) of the mold without flattening a sealing gasket ( 13 ), so as to attract the nozzle ( 10 ) and the wall (F) towards each other with an attraction force greater than the repulsion force due to the pressure of the blow-molding fluid.

FIELD OF THE INVENTION

The present invention relates to improvements made to blow moldinginstallations, or to stretch-blow molding installations that implement aspecial nozzle referred to as a “bell-nozzle” and that are formanufacturing receptacles from roughs or blanks of thermoplasticpolymer, in particular polyethylene terephthalate (PET), such aninstallation comprising a blow nozzle of the bell-nozzle type forblowing a fluid under pressure into a blank disposed in a cavity of amold, said nozzle having its end in the shape of a bell which issuitable, during blow-molding, for being pressed into leaktightend-to-end abutment against a wall of the mold while capping the neck ofthe blank that emerges from said wall against which said blank is inabutment via an annular collar while its body is engaged in said cavityof the mold.

DESCRIPTION OF THE PRIOR ART

A bell-nozzle blow-molding installation is described in document FR-A-2764 544. In that known arrangement, as is shown in particular in FIGS. 1and 2 of that document, the bell-shaped end portion of the nozzle issupported at the end of an elongate tubular body having a portion ofincreased diameter that forms a piston slidably received axially in astationary cylinder provided with end orifices for constituting feedsand discharges for a drive fluid. By means of that pneumatic drive, thebell of the nozzle can be brought into leaktight end-to-end contactagainst the wall of the mold for the purpose of performing theblow-molding operation, or after said operation, be moved in theopposite direction so as to bring it away from the mold.

Document FR-A-2 790 704 describes a bell-nozzle blow-moldinginstallation in which the nozzle is moved by toggle mechanical meansdriven by a side pneumatic actuator.

In both of those cases, the bell of the nozzle must be applied againstthe mold with a force greater than the repulsion force generated by thepressure of the blow-molding pressure (e.g. typically about 40×10⁵pascals (Pa)). As a result, the support of the mold and the support ofthe nozzle are subjected to very large reaction forces whose influenceis felt even more acutely since those supports are generallycantilevered out or have cantilevered-out portions; in particular it isusual for the nozzle to be supported by a transverse arm supported viaone of its ends.

The structural arrangements and the operating conditions of those knownblow-molding installations lead to the support members being reinforced,which results in increased weights and higher inertias for the movingparts, going against what is necessary for allowing the operating speedsof the machines to be increased as is desired by users.

SUMMARY OF THE INVENTION

An object of the invention is thus to propose an improved arrangementfor blow-molding machines equipped with bell-nozzles so that they areable to withstand operating throughputs that are high, or even that arehigher than those currently used, while also making provision, as far aspossible, to simplify the structure of the machine, in particular asregards the blow nozzle and the means for actuating it.

To these ends, a bell-nozzle blow-molding installation as mentioned inthe introduction is characterized, as arranged in accordance with theinvention, in that it further comprises means for securing the nozzle tosaid wall of the mold by releasable mutual attraction, which means canbe activated, after the nozzle has been brought into end-to-end contactwith said wall of the mold without flattening a sealing gasket, so as toattract the nozzle and said wall towards each other with an attractionforce greater than the repulsion force due to the pressure of theblow-molding fluid.

By means of the provisions specific to the invention, it is only betweenthe co-operating elements (wall of the mold/nozzle) that the securingforce is exerted, and said elements are attracted towards each other byimplementing suitable means. In such an arrangement, the respectivesupports for supporting the mold and for supporting the nozzle are nolonger subjected to high reaction forces as they are in prior devices.Since they only have to perform their support functions, the respectivesupports for the mold and for the nozzle need to be dimensioned only forperforming said support functions: they can thus be made in forms thatare lighter in weight than the prior structures, thereby reducing theirweights and thus significantly reducing their inertias, which is veryadvantageous for allowing higher operating speeds to be achieved.

Various types of embodiment are possible for such means for securing bymutual attraction.

Thus, it is possible to implement mechanical means. For example, suchmechanical means for securing by mutual attraction may comprise at leastone device for securing by fastening the nozzle to said mold wall, whichdevice comprises firstly at least one bar secured to said wall of themold and secondly at least one curved finger pivotally supported by thebell of the nozzle, said finger being of varying curvature and beingsuitable for being engaged under said bar with a force being generatedthat urges the nozzle and the wall of the mold towards each other. Aplurality of devices of this type (e.g. two) may be implemented,uniformly distributed over the peripheries of the mold and ofbell-nozzle.

Thus also, the means for securing by mutual attraction may be fluidmeans suitable for generating suction at the surface of the wall of themold facing the end wall of the bell of the nozzle. For example, in viewof the technological context of the installation whose controls areessentially of the pneumatic type, it is advantageous for the fluidmeans for securing by mutual attraction to be pneumatic means whichcomprise an annular groove formed in the wall of the mold and in whichat least one channel opens out in communication with means forgenerating suction, said annular groove having a diameter substantiallyequal to the diameter of the end wall of the bell of the nozzle that issituated facing it.

Thus also, the means for securing by mutual attraction may be magneticmeans. In practical manner, the magnetic means for securing by mutualattraction may comprise at least one magnetic device carried by thenozzle, said magnetic device having selective control means forestablishing or interrupting the magnetic flux, and a zone made of aferromagnetic material provided on said wall of the mold facing thenozzle. Admittedly, it is then possible to make provision for themagnetic device to comprise at least one permanent magnet supported bythe nozzle and a moving magnetic screen associated functionally withsaid magnet for allowing the magnetic flux from said magnet to pass orfor interrupting said magnetic flux. However, if it is desired to avoidhaving to use moving parts that can suffer from operating times that aretoo long in regard to the desired high operating speeds, it is possibleto use a magnetic device having a permanent magnet equipped with anelectrical control suitable for acting, when it is excited, to generatemagnetic flux that is approximately of the same magnitude and ofdirection opposite to the direction of the magnetic flux of thepermanent magnet. A plurality of magnetic devices may preferably bedistributed around the peripheries of the mold and of the nozzle.

Thus also, finally, in preferred manner, the means for securing bymutual attraction may be electromagnetic means which comprise at leastone electromagnet device having a coil associated with a core that aresupported by the nozzle and that are suitable for co-operatingfunctionally with the wall of the mold or a portion of said wall that ismade of a ferromagnetic material. Although it is possible to considerimplementing a plurality of electromagnet devices distributed around theperipheries of the mold and of the nozzle, it is however simpler andless constraining, in terms of weight and of overall size, to use asingle electromagnet device of annular shape mounted coaxially in thebell end of the nozzle.

It is common, in nozzle blow-molding installations concerned by theinvention, for the mold to be equipped with a removable neck plate thatis secured to said wall of the mold, and it is against said neck platethat the bell of the nozzle comes into leaktight end-to-end abutment.Such a steel neck plate is used in particular with molds made ofaluminum alloy, so as to reduce the wear due to contact with the bell ofthe nozzle, so as to ensure the surface abutting against the nozzle issmoother and longer-lasting and favorable to providing sealing ofgood-quality, and, by using interchangeable neck plates having centralorifices of various dimensions, so as to facilitate the use of the moldfor manufacturing receptacles provided with necks of various diameters.In which case, advantage is taken from the presence of the neck plate tomake it include the mold portion of the means for securing by mutualattraction. In particular, it is easy to equip the neck plate so that itis provided with the groove of the above-mentioned pneumatic means, and,above all, it is easy to make the neck plate from a ferromagneticmaterial that is suitable when implementing the above-mentioned magneticor electromagnetic means.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood on reading the followingdetailed description of certain embodiments given merely by way ofnon-limiting example. In the description, reference is given to theaccompanying drawings, in which:

FIG. 1 is a fragmentary section view of a mold and of a nozzle equippedwith mechanical fastening means making it possible for securing to beachieved by mutual attraction;

FIG. 2 is a fragmentary section view of a mold provided with a neckplate and of a nozzle that are provided with pneumatic means forsecuring by mutual attraction;

FIGS. 3 and 5 are fragmentary section views of a mold provided with aneck plate and of a nozzle that are provided with permanent-magnetmagnetic means for securing by mutual attraction with, respectively, anelectrical control and a moving-screen mechanical control; and

FIG. 4 is a fragmentary section view of a mold provided with a neckplate and of a nozzle that are provided with electromagnetic means forsecuring by mutual attraction.

DETAILED DESCRIPTION OF THE INVENTION

In the various figures of the accompanying drawings, only theco-operating portions of the mold and of the blow nozzle that arenecessary for understanding the invention are shown. In the figures,like elements or portions are designated by like reference numerals.

With reference firstly to FIG. 1, a mold 1 has a mold cavity 2 that hasthe same shape as a receptacle to be obtained by deforming a rough orblank (e.g. a preform) 3. In particular the mold is of the hinged typeor bill-fold type. In which case, the mold 1 comprises two half-molds 4provided with respective cavity-forming recesses 5 which, when broughttogether (when the mold is closed) define the mold cavity 2, or most ofsaid cavity when the mold is further provided with a complementary partprovided with the cavity-forming recess for the bottom of thereceptacle.

The mold 2 has an external wall F (top wall in FIG. 1) in which the moldcavity 2 opens out via a passageway 6 (neck passageway) via which theblank 3 is engaged. The neck 7 of the blank 3 has its final shape andits final dimensions, and it bears via an annular collar 8 against thewall F of the mold. Only the body 9 of the blank 3 extends inside themold cavity 2.

As regards the blow means, only the end portion of the blow nozzle 10 isshown. The bell-shaped end portion 11 is supported by a tubular body 12serving to feed in the fluid under pressure. The annular end wall of thebell 11 is equipped with an annular sealing gasket 13. The bell 11 isshaped and dimensioned so that, when it is brought into end-to-endabutment against the wall F of the mold, it caps the neck 7 of the blankprojecting above said wall F.

The support means (not shown) for supporting the nozzle 10 are arrangedto make it possible for the nozzle to move axially in both directions(arrow 15) so as to bring said nozzle against the mold for theblow-molding operation or so as to move it away therefrom forloading/unloading the mold.

FIG. 1 also shows a draw rod 14 that is engaged coaxially through thetubular body 12 of the bell 11 and that extends to the point of touchingthe inside of the bottom of the blank 3 so that, by being moved axiallytowards the bottom of the mold, it mechanically draws the body of theblank 3 at the same time as said body is being expanded pneumaticallyduring the blow-molding process.

The details of how the blow nozzle is arranged and of how it operatesare described and shown in Document FR-A-2 764 544.

In the prior arrangements, it is the support means for supporting thenozzle 10 that push the nozzle 10 against the wall F of the mold with aforce greater than the repulsion force generated, during blow-molding,by the very high (e.g. typically about 40×10⁵ Pa) pressure of theblow-molding fluid (in general air) that is present in the chamberdefined by the bell 11 closed by the wall F. The thrust force developedby the support means of the nozzle generates reaction forces both on thesupport of the mold and on the support of the nozzle, which reactionforces are even more problematic mechanically since said supports aregenerally cantilevered out and are therefore overdimensioned.

In order to avoid these drawbacks, the invention thus proposes toreplace the thrust force whereby the nozzle is pushed against the wall Fof the mold with a mutual attraction force whereby the nozzle (moreprecisely the bell 11 of the nozzle) and the wall F of the mold aremutually attracted, so that there are then no reaction forces at thesupports, and said supports can then be lighter in weight.

Under these conditions, the support means of the nozzle 10, whichsupport means move the nozzle axially in both directions 15 merely haveto bring the end face of the bell 11 into contact with the wall F,without flattening the gasket 13 (position shown in FIG. 1). It is thenthe means for securing by mutual attraction that are provided on thewall F and/or on the nozzle 10, and in particular on the bell 11thereof, that put the bell 11 into end-to-end leaktight abutment againstthe wall F with an attraction force greater than the repulsion force ofthe blow-molding fluid.

The means for securing by mutual attraction can be of any desirable typesuitable for the function to be provided, in particular as regardsmechanical resistance to the high repulsion force that tends to push thebell 11 away, and as regards the speed of operation in the context ofhigh production throughput.

The means for securing by mutual attraction can be mechanical means 16₁, one possible embodiment of which is shown in FIG. 1. In order toclamp the bell 11 uniformly over its entire periphery, a plurality ofmechanical means 16 ₁ can be provided, each of which is constituted by amechanical clamping device, which means are distributed peripherally(two diametrically opposite ones are shown in FIG. 1).

Each clamping device 16 ₁ comprises a bar 17 secured to the wall F ofthe mold. The bar 17 can project relative to the wall F as shown in FIG.1, or else be set back into a recess provided in the wall F.

On the outside wall of the bell 11, a projecting yoke 18 supports acurved finger 20 which is received to pivot freely on a pivot 19 andwhich has its free end 21 facing the bar 17 and positioned immediatelytherebelow, as shown in FIG. 1, when the clamping device is not active.

At its opposite end situated on the other side of the pivot 19, thecurved finger 20 is hinged to the end of a drive rod 22 which is drivenapproximately parallel to the axis of the nozzle (double-headed arrow23) by control means (not shown).

By giving the bottom edge 24 of the finger 20 a suitable curvature ofgradually decreasing radius, moving the rod 22 upwards causes the curvedfinger 20 to engage under the bar 17 and, by means of moving contact ofthe edge 24 of the finger against the underside of the bar 17, powerfulmechanical clamping is obtained whereby the bell 11 of the nozzle isclamped powerfully against the wall F of the mold.

The means for securing by mutual attraction can also be suctionpneumatic means 16 ₂, a possible embodiment of which is shown in FIG. 2.

At its base, the bell 11 is provided with an annular ring 25 that isshaped in a manner such as to have a wider end face 26.

The mold 1 is provided with an annular groove 27 set back into its wallF concentrically relative to the neck passageway 6. The groove 27 isdimensioned such that it extends facing said wider end face 26 of theannular ring 25 of the bell 11, and it has a width slightly smaller thanthe width of said end face 26.

Starting from the groove 27, at least one channel 28 extends that is setback into the mold 1 and that opens out in a wall of the mold, e.g. thewall F, via a coupling 29 to which a duct 30 is connected for linking toa suction pump 31.

When the bell 11 is brought into the immediate vicinity of the wall F,connecting (at 30 a, e.g. via an electrically-controlled,electro-pneumatically controlled, or magnetically controlled connection)the duct 30 to the suction pump 31 establishes a vacuum in the groove 27that is suitable for attracting the bell 11, with the end face 26covering the opening in the groove in leaktight manner. The attractionforce whereby the bell 11 of the nozzle 10 is attracted against the wallF of the mold 1 depends on the area of mutual contact between the groove27 and the end face 26, i.e. on the diameter and on the width of thegroove and on the magnitude of the suction generated by the pump 31.

In order to avoid having to form the groove 27 and the channel 28directly in the thickness of the mold 1, it is advantageously possibleto make provision for them to be implemented in combination with a neckplate 32 of the type commonly used in this type of mold havingbell-nozzle blow means, in order to enable the bell to bed down in morestable and more leaktight manner, and in order to enable receptacleshaving various neck diameters to be manufactured without modifying themold itself. In the mold considered herein, the neck plate 32 is made upof two half-plates 33 removably set into respective ones of twocountersunk portions provided in respective ones of the two half molds4. The groove 27 and the channel 28 are then formed in the two neckhalf-plates 31.

The means for securing by mutual attraction can also be magnetic means16 ₃, one possible embodiment of which is shown in FIG. 3.

The bell 11 supports, e.g. by means of radially-projecting tabs 34,magnetic devices or “magnetic suction cups” 35 that can, as shown, beelectrically controlled, such as those available commercially under thereference 01320 from Binder Magnetic. Each of these magnetic devices 35comprises a permanent magnet generating a magnetic field between thecentral pole and the periphery of the holding surface 36. The devicefurther comprises a switch-off coil (not shown) connected via wires 37to a DC voltage source, which coil, when it is excited, generates amagnetic field of poles opposite to the poles of the permanent magnet,which field substantially neutralizes the magnetic field of thepermanent magnet.

By means of such magnetic means 16 ₃ having magnetic suction cup devicesthat are electrically controlled, and of which, for example, a plurality(two, three or four) are disposed over the periphery of the bell, it ispossible to secure the bell 11 of the nozzle 10 to the mold 1 by mutualattraction and in releasable manner.

In order to close the magnetic circuit when the mold 1 is made of anon-magnetic metal (e.g. of aluminum or of an aluminum alloy), it ispossible to provide a neck plate 32 as mentioned above for the precedingembodiment, the neck plate 32 being made of steel.

In a manner that is preferred for reasons of simplicity ofimplementation and of suitability for operation at high throughput, themeans for securing by mutual attraction can also be electromagneticmeans 16 ₄, one possible embodiment of which is shown in FIG. 4.

The electromagnetic means 16 ₄ shown are constituted by anelectromagnetic suction cup 38 of annular structure that is integratedcoaxially into the end of the bell 11, which end is arranged in the formof an annular skirt and made of a non-magnetic material. Theelectromagnetic suction cup 38 comprises an annular magnetic 39, e.g.made of an aluminum—nickel—cobalt alloy (AlNiCo), surrounded by a coil40. In front of the magnet surrounded by its coil, a core 41 made ofsteel is disposed that is surrounded by a ring 42, e.g. made of aneodymium—iron—boron (NdFeB) alloy. In the end face of the steel core41, the annular sealing gasket 13 is supported by any suitable means.All of the component parts can be assembled in the bell 11 by means ofbolts 43.

Implementing such an electromagnetic suction cup 38 is particularlyadvantageous when the mold 1 is equipped with a neck plate 32 in themanner explained above, said neck plate then being made of aferromagnetic material, in particular of steel.

For exciting the coil 40, said coil is connected via wires 44 to anelectrical power source S via a switch 45 with which a control device 46is functionally associated.

The advantage of this solution lies in the absence of moving parts: itis thus possible, without any significant problem, to obtainhigh-throughput operation which is increasingly required by users.

Also in the context of implementing magnetic means, it is possible toconsider using magnetic means 165 comprising magnets 47 that can bemasked by screens 48 which can be moved by a suitable drive member 49 asshown in FIG. 4.

It can be understood that each of the types—mechanical, pneumatic,magnetic, electromagnetic—of securing means described and shown above isgiven merely by way of example, and that, for each type, other solutionscan be implemented while remaining within the ambit of the invention.Each securing device that is described above—regardless of whether it isof the mechanical, fluid, magnetic, or electromagnetic type—includescontrol means that can be of any design that is desirable, in particularwith regard to the controls used in the remainder of the installation:mechanical means (in particular a cam/wheel system that is very commonin these installations) or electropneumatic means, or electrical means(in association with a management unit for managing the installation asa whole).

1. A blow molding or stretch-blow molding installation for manufacturingreceptacles from blanks of thermoplastic polymer, in particularpolyethylene terephthalate (PET), said installation comprising a blownozzle of the bell-nozzle type for blowing a fluid under pressure into ablank disposed in a cavity of a mold, said nozzle having its end in theshape of a bell which is suitable, during blow-molding, for beingpressed into leaktight end-to-end abutment against a wall of the moldwhile capping the neck of the blank that emerges from said wall againstwhich said blank is in abutment via an annular collar while its body isengaged in said cavity of the mold; wherein said installation comprisesmeans for securing the nozzle to said wall of the mold by releasablemutual attraction, which means can be activated, after the nozzle hasbeen brought into end-to-end contact with said wall of the mold withoutflattening a sealing gasket, so as to attract the nozzle and said walltowards each other with an attraction force greater than the repulsionforce due to the pressure of the blow-molding fluid.
 2. A blow-moldinginstallation according to claim 1, wherein the means for securing bymutual attraction are mechanical means.
 3. A blow-molding installationaccording to claim 2, wherein the mechanical means for securing bymutual attraction comprise at least one device for securing by fasteningthe nozzle to said mold wall, which device comprises firstly at leastone bar secured to said wall of the mold and secondly at least onecurved finger pivotally supported by the bell of the nozzle, said fingerbeing of varying curvature and being suitable for being engaged undersaid bar with a force being generated that urges the nozzle and the wallof the mold towards each other.
 4. A blow-molding installation accordingto claim 1, wherein the means for securing by mutual attraction arefluid means suitable for generating suction at the surface of the wallof the mold facing the end wall of the bell of the nozzle.
 5. Ablow-molding installation according to claim 4, wherein the fluid meansfor securing by mutual attraction are pneumatic means which comprise anannular groove formed in the wall of the mold and in which at least onechannel opens out in communication with means for generating suction,said annular groove having a diameter substantially equal to thediameter of the end wall of the bell of the nozzle that is situatedfacing it.
 6. A blow-molding installation according to claim 1, whereinthe means for securing by mutual attraction are magnetic means.
 7. Ablow-molding installation according to claim 6, wherein the magneticmeans for securing by mutual attraction comprise at least one magneticdevice carried by the nozzle, said magnetic device having selectivecontrol means for establishing or interrupting the magnetic flux, and azone made of a ferromagnetic material provided on said wall of the moldfacing the nozzle.
 8. A blow-molding installation according to claim 7,wherein the magnetic device comprises at least one permanent magnetsupported by the nozzle and a moving magnetic screen associatedfunctionally with said magnet for allowing the magnetic flux from saidmagnet to pass or for interrupting said magnetic flux.
 9. A blow-moldinginstallation according to claim 7, wherein the magnetic device comprisesat least one permanent magnet supported by the nozzle and an electricalcontrol associated functionally with said magnet and suitable foracting, when it is excited, to generate magnetic flux substantiallycanceling out the magnetic flux from the magnet.
 10. A blow-moldinginstallation according to claim 1, wherein the means for securing bymutual attraction are electromagnetic means which comprise at least oneelectromagnet supported by the nozzle and which are suitable forco-operating functionally with the wall of the mold or a portion of saidwall that is made of a ferromagnetic material, in particular steel. 11.A blow-molding installation according to claim 1, wherein the mold isequipped with a removable neck plate that is secured to said wall of themold, and wherein, on the mold, the means for securing by mutualattraction are provided in said neck plate.